The volume scattering function (VSF) describes the angular distribution of the light scattering that results from an incident beam interacting with a small volume of water. Knowledge of the VSF of marine particles is of primary importance for remote sensing and marine biogeochemical applications. VSF measurements have been rarely carried out because of practical difficulties to build an appropriate instrumentation. The main challenging tasks in the development of such instruments consist in (i) the measurements of the VSF at small (<1°) and large (> 170°) scattering angles and (ii) the minimization of the influence of the photons scattered in the backward direction by the instrument itself on the photons backscattered by the sample. We are developing a new instrument (so-called POLVSM) capable of measuring the Mueller scattering matrix elements over a wide range of scattering angles (typically from 1° to 178°). The device is designed to drastically reduce the stray light induced by the instrument itself in the backward direction. The POLVSM instrument provides the polarized volume scattering function of the particles which has not been measured for two decades. Here, we present the development of the instrument, the calibration experiments and the preliminary tests carried out in a coastal environment.

Funding and development strategy

The PolVSM instrument has been designed by the team and is being built in our lab with the help of the Observatoire Côte d’Azur. The concept of the instrument, and especially the design of both periscope, has been patented.